Method for producing phosgene

Patent metadata

Field	Value
Publication number	US-12391557-B2
Application number	US-202017605737-A
Country	US
Kind code	B2
Filing date	Apr 14, 2020
Priority date	Apr 25, 2019
Publication date	Aug 19, 2025
Grant date	Aug 19, 2025

Abstract

The present invention relates to a process for preparing phosgene by reacting chlorine with carbon monoxide over an activated carbon catalyst, wherein the content of chlorine oxides in the chlorine feed stream is low, to an apparatus for preparation of phosgene and to the use of the phosgene prepared by the process of the invention.

First claim

The invention claimed is:

1. A process for preparing phosgene comprising
a) providing a chlorine feed stream having a content of chlorine oxides of not more than 130 ppm by volume, wherein
i) chlorine is prepared by electrolyzing an aqueous solution of sodium chloride under conditions under which chlorine is obtained with a chlorine oxide content of not more than 130 ppm by volume, or
ii) chlorine having a chlorine oxide of more than 130 ppm by volume is subjected to a workup by which the content of chlorine oxides is reduced to a value of not more than 130 ppm by volume, or
iii) a first chlorine gas stream having a chlorine oxide content of more than 130 ppm by volume is mixed with a second chlorine gas stream having a chlorine oxide content of less than 130 ppm by volume in such a ratio as to result in a chlorine feed stream having a content of chlorine oxides of not more than 130 ppm by volume, or
iv) the chlorine is prepared by using a process other than the electrolysis of an aqueous solution of sodium chloride in which chlorine with a chlorine oxide content of not more than 130 ppm by volume is obtained,
b) subjecting the chlorine feed stream provided in step a) to a catalytic reaction with carbon monoxide over an activated carbon catalyst in at least one reactor.

2. The process according to claim 1 , wherein, in i),
i1) an aqueous stream having a reduced sodium chloride content and an elevated sodium chlorate content compared to the aqueous sodium chloride solution supplied to the anode chamber is withdrawn from the anode chamber of the electrolysis cell used for electrolysis of the aqueous sodium chloride solution,
i2) the aqueous stream withdrawn from the anode chamber is partly or fully discharged, or at least a portion of the sodium chlorate present is removed from the aqueous stream withdrawn from the anode chamber, and
i3) the sodium chloride content of the portion of the aqueous stream withdrawn from the anode chamber that was not discharged in step i2) is increased and it is recycled into the anode chamber.

3. The process according to claim 2 , wherein, in i2), at least a portion of the sodium chlorate present in the aqueous stream withdrawn from the anode chamber is removed by admixing the stream with acid.

4. The process according to claim 2 , wherein at least a portion of the aqueous stream withdrawn from the anode chamber is subjected to a treatment to reduce the content of chlorine oxides present therein by UV irradiation.

5. The process according to claim 1 , wherein, in ii), the chlorine, for workup, is subjected to a thermal, chemical catalytic, or photochemical treatment, to obtain a chlorine feed stream having a content of chlorine oxides of not more than 130 ppm by volume.

6. The process according to claim 1 , wherein chlorine prepared by HCI electrolysis, Deacon process or the KEL chlorine process is used as second chlorine gas stream in step iii), or wherein chlorine prepared by HCI electrolysis, Deacon process or the KEL chlorine process is used in step iv).

7. The process according to claim 1 , wherein the chlorine oxide comprises chlorine dioxide or consists of chlorine dioxide.

8. The process according to claim 1 , wherein the phosgene synthesis is conducted in at least one shell and tube reactor with activated carbon catalyst present in the tubes thereof.

9. The process according to claim 1 , wherein the phosgene synthesis is effected in at least one shell and tube reactor, and the reactor tubes are cooled by contacting with a liquid heat carrier or by means of evaporative cooling.

10. The process according to claim 9 , wherein cooling is effected using a liquid heat carrier which is guided in cocurrent or in countercurrent to the flow direction of the gases reacting in the reactor tubes.

11. The process according to claim 9 , wherein the shell and tube reactor has a shell space through which the heat carrier flows, and the shell space is divided into at least two zones that are supplied separately with liquid or boiling heat carrier for cooling.

12. The process according to claim 1 , wherein the activated carbon used is prepared by pyrolysis of a natural raw material, wherein the activated carbon catalyst is in the form of spheres, cylindrical strands, platelets or rings.

13. A process for preparing phosgene as defined in claim 1 , using an apparatus for preparation of phosgene, comprising:
a unit for reducing the chlorine oxide content in a chlorine oxide-containing chlorine feed stream having an inlet for the chlorine feed stream and an outlet for the chlorine oxide-depleted chlorine feed stream, and
a shell and tube reactor with reactor tubes containing an activated carbon catalyst bed, wherein the shell and tube reactor has an inlet for the chlorine oxide-depleted chlorine feed stream and an outlet for a phosgene-containing product stream, wherein the chlorine oxide-depleted chlorine feed stream is mixed with a carbon monoxide feed stream before entering the shell and tube reactor;

wherein the chlorine oxide content in the chlorine feed stream is determined and the temperature of the chlorine feed stream is controlled as a function of the chlorine oxide content such that the content of chlorine oxides at the inlet to the phosgene reactor is not more than 130 ppm by volume.

Assignees

• Basf Se

Inventors

• Mattke Torsten
• Olbert Gerhard
• Gauer Jochen
• Thiele Kai
• Vandewalle Koenraad
• Ferbitz Jens
• Van Den Abeel Peter

Classifications

• C25B15/08

  Supplying or removing reactants or electrolytes; Regeneration of electrolytes · CPC title

• C25B1/46

  in diaphragm cells · CPC title

• C25B1/34

  Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis · CPC title

• C25B1/26 Primary

  Chlorine; Compounds thereof (by simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine C25B1/34) · CPC title

• C01B32/80 Primary

  Phosgene · CPC title